1. Field of the Invention
The present invention relates to a key depression number processing system for a keyboard circuit which is limited in its maximal number of tones that can be produced. In the case where the number of simultaneous key depressions is larger than the maximal number of tones that can be produced, high-pitched and low-pitched tones are preferentially produced omitting intermediate tones, thereby making the limitation on the maximal number of tones unnoticeable.
2. Description of the Prior Art
In conventional key depression number processing systems for a digital keyboard circuit, there have been employed such techniques as "preferential tone production of earlier depressend keys", "preferential tone production of later depressed keys", "preferential high-pitched tone production", "preferential low-pitched tone production" and so forth, in the case where the number of simultaneous key depressions is larger than a maximal number of tones that can be produced. With any of these systems, however, when keys are simultaneously depressed in excess of the limited maximal tones, unnatural sounding tones inevitably resulted.
It is known that human ears are sensitive to the addition of low-pitched or high-pitched sounds to a group of sounds being produced but not so sensitive to the addition or subtraction of intermediate sounds. The present invention is based on an idea of preferentially producing low-pitched and high-pitched depressed key tones omitting the intermediate depressed key tones in the case where the number of simultaneous key depressions is larger than the maximal number of tones that can be produced.